1. Field of the Invention
This invention relates to a field emission element, and more particularly to a field emission element which is useful as an electron source for various kinds of devices such as a display device, a light source, an amplification element, a high-speed switching element, a sensor and the like.
2. Discussion of the Background
The manufacturing and structure of a conventional field emission element (FEC) will be described in connection with a Spindt-type (vertical type) field emission element shown in FIGS. 4a to 4e.
In manufacturing of the conventional field emission element of the Spindt type, as shown in FIG. 4a, a cathode electrode 101, an insulating layer 102 and a gate electrode layer 103 are laminatedly deposited in that order on an insulating substrate 100.
Then, a resist is deposited on the gate electrode layer 103 and exposure of a gate pattern of 1 .mu.m in diameter is successively carried out by means of light beams or electron beams. Subsequently, a portion of the resist which has been subject to exposure is removed and the gate electrode layer 103 and insulating layer 102 are subject to etching, thereby to form a gate 104 and a hole 105 as shown in FIG. 4b.
Subsequently, the resist is removed and then an Al layer 106 is obliquely downwardly deposited on a surface of the insulating substrate 100 while the insulating substrate 100 is rotated in the same plane, resulting in an opening of the gate 104 being contracted and a peel layer being formed as shown in FIG. 4c.
Next, as shown in FIG. 4d, the deposition of an emitter material 107 on the Al layer 106 is carried out vertically downwardly toward the substrate 100 to form an emitter 108 of a cone-like shape in the hole 105.
Thereafter, as shown in FIG. 4e, the obliquely deposited Al layer 106 and unnecessary emitter material 107 are removed, leading to the field emission element.
In the conventional field emission element formed as described above, a metal of a high melting point which has a reduced work function, such as Mo or the like is used as a material for the emitter and gate. Unfortunately, the use of such a metal is made without consideration as to the reaction of Mo or the like with oxygen atoms or molecules of a compound containing oxygen during operation of the field emission element in a vacuum atmosphere and as to an optimum combination of materials for the emitter and gate.